Plot Synopsis

When Leo invites his hip and trendy ex-girlfriend to a friendly dinner party, Grace turns to Will, Jack and Karen to round out the guest list and keep the night running smoothly. However, when Leo's ex turns out to be the only girl Will ever slept with, Grace's jealousy gets the better of her. Meanwhile, Karen discovers Lorraine's teacup poodle Chompers hiding in Stan's closet and searches for a new owner for the puppy.

Cast

Eric McCormack (Will Truman)

Debra Messing (Grace Adler)

Sean Hayes (Jack McFarland)

Megan Mullally (Karen Walker)

Guest Cast

Harry Connick Jr. (Dr. Leo Markus)

Mira Sorvino (Diane)

Notes

We first learned of Diane in the season 3 flashback episode "Lows in the Mid-Eighties". She was briefly seen — played by writer's assistant Lisa Borgnes.

Chompers (who is a teacup poodle) ends up with Diane at the end of the episode.